Dear colleagues,
On behalf of my co-authors, I am pleased to announce our recent publication in
Oceans as part of the Special Issue Marine Mammals in a Changing World, 3rd
Edition:
Mills, E.M.M., Piwetz, S., & Orbach, D.N. (2025). Dolphins
‘Orient-Against-Current’: Foraging in Dredged Channels. Oceans, 6(4), 78.
https://doi.org/10.3390/oceans6040078
ABSTRACT
Bottlenose dolphins (Tursiops sp.) are opportunistic foragers with global
distributions that utilize diverse feeding tactics based on environmental
factors, habitat features, prey behavior, group dynamics, and genetics. We
describe a unique foraging tactic regularly observed in the confluence of
dredged shipping channels with high anthropogenic disturbance, and explore
potential abiotic (temporal, tidal, habitat) drivers of the behavior. A
shore-based digital theodolite was used from 2021 to 2022 to observe common
bottlenose dolphins (T. truncatus) foraging within a current in a technique we
term Orient-Against-Current (OAC). During OAC, dolphins position themselves
facing into the flow of a current, swimming at a speed to maintain a stationary
position within the current, and feed while prey move with the current towards
them. Orient-Against-Current occurred in all seasons and throughout daylight
hours, particularly during the winter and spring. Dolphins engaged in OAC
during ebb tides and intermediate current speeds (1–2 knots), but not during
slack tides. As OAC occurred closer to shoreline structures (i.e., seawalls,
concrete blocks) than to mangroves and natural seagrass beds, it appears that
hard human-engineered structures aid in prey capture during OAC. Knowledge of
dolphin foraging techniques can aid in understanding behavioral plasticity
shaped by anthropogenically altered environments in industrialized coastal
areas.
The article is open access and freely available:
https://www.mdpi.com/2673-1924/6/4/78
Best regards,
Eliza Mills
Associate Consultant | Federal Health & Sciences
Environmental Systems Research Institute (Esri)
Vienna, VA, USA
[email protected]
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